Art of recording sound or other vibratory energy



Y van. 7, 1930.

C. A. WHITSETT ART OF RECORDING SOUND OR OTHER VIBRATORY ENERGY Filed May 22. 1922 2 Sheets-SheetI Jan. 7, 19.30. C, A, wHlTsET-r 1,742,490

ART 0F RECORDING SOUND OR OTHER VIBRATORY ENERGY Filed May 22. 1922 2 Sheets-Sheet 2 EIDDDDCIDD .Fm/emr amm a Wm sTTEs PATENT CAMERON A. W'HITSETT, OF CHICAGO, ILLINOIS .ABT OF RECORDING SOUND 0R OTHER VIBRATORY ENERGY Application led May 22,

rlhe present invention relates to the art of recording sound or other vibratory energy. The primary object of the invention is to pro- Vide an improved method of and apparatus `for recording sound and other Vibratory energy wherein the energy undulations are recorded electrically, preferably by means of a high potential spark, which has the advan- .tage of being an aperiodic stylus or recordproducing medium. ThisI quality of aperiodicity or freedom from dampening influences follows from the non-physical or intangible connection between the diaphragm or other sound responsive means and the record surface. In the prior methods of producing wax records either by a lateral cut or hill-and-dale undulations, the drag or physical contact of the recording stylus on therecording surface tends to dampen the oscillations of the recording diaphragm, lends an undesirable periodicity to the diaphragm, and diminishes its responsiveness to feeble `sound waves. The recording medium in the present instance, consisting of an electric spark, has no measurable inertia and hence cannot impose this dampening influence on the diaphragm. This method of recording together with the method of reproducing from the record thus made, permits of infinite v variations in intensity, expression, tone quality, etc. either at the time the record is being made, or subsequently when the record is being reproduced. The present electrical method of recording sound also permits the record to be made in the form ofa continuous tape or strip which may be wound on reels or the like. By virtue of this continuous tape characteristic of the record, records of very great length can be made without great bulk or .inconvenience in size. This contrasts sharply with the ordinary waX or mechanical record, wherein the length of record is imperatively limited by the size of the disc or cylinder, and where it would be impracticable to get a complete lecture, opera, or the like on one record.

In the accompanying drawings illustrating a preferred embodiment of my invention;

r Fig. 1 is a vertical sectional View of one form of my improved sound recording mech- 1922. Serial No. 562,569.

anism characterized by the electrical recording of sound on a continuous tape, this figure being a sectional view taken approximately on the plane of the line 1 1 of igure 2;

Fig. 2 is a horizontal view takenapproximately on the plane of the line 2--2 of Figure 1;

Fig. Sis a fragmentary detail section of a modification;

Figure 4 is a vertical sectional View of a modified arrangement of sound recording mechanism;

Fig. 5 is a fragmentary illustration of a portion of the record tape, showing the line of perforations exaggerated;

Fig. 6 is a similar view illustrating another method of producing a tape form of record by an electrical discharge.;

Fig. 7 is another fragmentary view illustrating how my improved vsound recording method can be utilized in producing a sound record along the edge of a motion picture film, and r Fig. 8 is a diagrammatic view illustrating how the movement of the electrode stylus may be effected electrically, and also illustrating how the recording mechanism can be designed to produce a varying size of perforation in the record.

Referring noW to one preferred embodiment of the invention illustrated in Figs. 1 and 2, the recording apparatus is mounted on a base plate 51, from which rise two standards 52 and 53 in spaced relation. Both standards have bearings for two superposed shafts 54 and 55. The upper shaft 54 is adapted to rotatably support the feeding reel 56, and the lower shaft 55 is adapted to drive a take-up reel 57. The tape designated t is tial current employed for perforating the tape.

From the electrode 61, the tape is drawn down over a driving or pulling roller 63 which is journaled between the standardsl 52 and 59 adjacent the horizontal aXis of the shaft 55. Cooperatino with the pulling roller 63 is a compression roller 64, the bearings of which are supported by compression springs 65 in the standards 52 and 59, whereby the roller 64 is normally forced up against the bottom ofthe pulling roller 63 under resilient pressure. This Ainsures the maintenance of an effective pulling tension on the tape by the roller 63, either or both'of these rollers preferably having a rubber or other resilient surface for maintaining an effective grip on the tape. From the pulling roller 63 the tape is drawn inwardly onto the takeup reel 57, whichis driven simultaneously with the roller 63.

The driving mechanism comprises a hori zontal shaft 66 which is supported in bearings 67 and 68 between the two standards 52 and 53. A. worm wheel 69 on the end of the shaft- 66 meshes with a worm 71 which is provided on the portion of roller shaft 63 eX-' tending between the standards 52 and 53. rl"he pitch angle of the teeth of the worm Wheel 69 and worm 71 is such that the worm wheel is operative to drived the pulling roller at an accelerated rate of speed,` which speed is always maintained constant, however, in order to preserve the uniformity of the record on the tape.

A worm wheel 72 substantially similar to the worm wheel .69, is also mounted on the shaft 66 in position to drive the worm 73 which is provided on the shaft 55 intermediate the standards 52 and 53. For uniformity of parts the worm wheels 69 and 72, and the worms 71 and 73 can be substantial duplicates, whereby l the shaft 66 is operative to drive the roller 63 and shaft '55 at the same speed.

The driving element 74 for driving the shaft 66 is intended to be representative of any preferred driving element, such as, an electric motor, or a multi-drum spring motor, the latter possessing the advantage of being very quiet and substantially vibrationless in its operation.

The two reels 56 and 57 are preferably of light, sheet metal construction, the outer edges of the reel flanges being beveled to guide and prevent injury tocthe tape. The

take-up reel 57 is illustrated with a slot 75 in its hub 57 for detachably securing the end of the tape to the hub of the reel, it being obvious that any other equivalent means may be employed. The circumference of the hub 57 is preferably slightly larger than the circumference of the pulling roller 63, so that from the very start the take-up reel will tend to draw the tape faster than the positively pulling roller 63 supplies it. It will be obvious that'as the circumference of the wound portion on the take-up reel increases, there will be a tendency for the take-up reel to wind up the tape at a higher rate than the roller 63 feeds the same. To take care of this condition I propose driving the take-up reel 57 through a spring arm 76 which is adapted to be swung to resiliently bear against the outer side of the reel. This arm is rigidly secured at its inner end to a hub member 77, which is pivotedin a diametrical slot 78 in the end of the shaft 55. This hub member is pivoted on a pin 7 9, and when the spring arm 76 is swung over to bear against the reel, this hub is locked in position by a spring pressed plunger 81 engaging in a notch 82 in the periphery of the hub member. An adjusting screw 83 affords adjustment of the driving pressure exerted through the spring arm. When the spring arm is swung out into alignment with the shaft 55, all parts moving therewith are brought Within the confines of the shaft in the slot 78, so that the reel can be slipped over the spring arm and onto the shaft 55. The pressure of the spring arm 76 resiliently holds thc reel up against the hub 84 on the standard 52, and thus retains the reel in proper alignment at all times.

I also contemplate mounting a spring arm 76 in the shaft 54, the shaft 54 and spring arm 7 6 being stationary in this instance, whereby the spring arm would exert a retarding impulse on the reel so that the tape would be maintained taut at all times. It will, of course, be understood, that the provision of the reel 56 is merely illustrative for the purposes of the present disclosure, inasmuch as a large, continuous supply roll of tape may be employed in lieu of the reel 56.

The record is produced by the perforating action of an electric spark which is drawn between the electrode 61 and an acoustically vibrated electrode 85. The function of the late the electric spark back and forth across the moving paper tape in accordance with the vibrations of a diaphragm 86, and it will be evident that this vibrating electrode'may employ any one of numerous congurations and methods of operation for performing this function. In Figures 2 and 3 the electrode is illustrated as being of curved configuration, pivoted preferably at one end by pivot spindles 90-90. These pivot spindles referably extend considerably' above and below the vibrating electrode to which they are rigidly secured, so Aas to reduce the radial load imposed by the extending electrode u pon the bearing support in the bearings 87. These iis bearings are preferably mounted in brackets l 88 of insulating material, so that the bearings will not have to carry any current flow which might scar the bearing surfaces:

. The diaphragm 86 is of any suitable oonstruction, and is preferably mounted in a sound concentrating horn 89. Extending from the rear of the diaphragm 86 is a pivot lug 91 which has pivotal connection at 92 with a. short lever arm 93 of the vibrating electrode. Where the diaphragm is constructed of metal, it can be connected directly to the other side of the high potential circuit, as thru the binding post 94, for direct conduction thru the pivot lug 91 to the vibrating electrode 85; or where the diaphragm is constructed of mica or some other non-conducting material, a suitable wire or conductor may be extended to the pivot lug 91 or to the electrode 85 in any other suitable manner.

The approximate amplitude of movement of the vibrating electrode 85 is represented bythe two dotted line positions shown in Figure 2. lt will be obvious that by virtue of the multiplication of movement obtained thru the short lever arm 93, this amplitude of movement of the electrode is secured with a very small movement of the diaphragm 86. -When the diaphragm 86 is at the inner limit of its movement the heel of the electrodewhich may be considered that point adjacent the pivot 8G-is in closest proximity to the tape and stationary electrode 61. Consequently for this position of the diaphragm, the record made by the electric spark will be confined to the edge of the tape adjacent this heel of the electrode. Conversely, when the diaphragm is at the outer limit of this movement the toe of the vibrating electrode will be swung into close proximity to the tape and electrode G1, so that for this position of the diaphragm, the perforated record will be confined to the opposite edge of the paper tape. An intermediate position of the diaphragm will present an intermediate portion of the electrode 85 into closest proximity to the electrode 61, and hence the record will at this time be confined to the intermediate portion of the tape. lt will be obvious, therefore,

that the vibrations of the diaphragm 86 will swing successive points along thelength of the moving electrode into closest proximity to the stationary electrode in accordance with the intensity of the sound and the amplitude of movement of the diaphragm.

rl`he high potential current may be either pulsating or alternating, being preferably of relatively high frequency so that the successive perforations in either the straight or wavy portions of the record will be grouped closely together, even with a relatively high speed of the tape. The current value of the spark can be conveniently regulated in any suitable manner for obtaining any size perforation desired. For example, by utilizing a discharge of relatively high current value, a larger perforation may be obtained, and. of course, by reducing the current value the converse is true, thus enabling the size of perforation in the record to be conveniently regulated which may be very desirable for diiferent classes of records, or for obtaining different affects in reproduction. For example, if it is desired that a certain portion of the record reproduce in a louder tone the current flow may be increased by suitable manipulation of the resistance 95, so that the perforations in this particular portion of the record will be larger. These larger perforations may be utilized for decreasing the rethe rapid vibrating motion of this electrode towards and away from the electrode 61. By virtue of the horizontal disposal of the' vibrating electrode 85 and stationary electrode 01 any heat generated by the spark cannot influence the spark and cause it to rise and distort the record such as would possibly be the case if the electrodes were disposed in a vertical plane. The sparking edge of each electrode is preferably drawn to a taper so that the spark will be drawn between tWo sharp lines. rlhe vibrating electrode 85 and pivot spindles 86 are of very light construction so as to minimize the inertia of these moving parts and thereby minimize the dampening action of these parts on the diaphragm 86. It will be apparent that if the f vibrating electrode exhibits a tendency to sus tain vibration, the outer end thereof, or any suitable part, can be damped by a Vane 101. Or, in lieu thereof, the vibrating electrode can be damped by a line tension spring 102, (see Fig. 3).

It will be apparent that the spark is incapable of transmitting any measurable inertia between the record tape and the diaphragm. Thus, the cutting or making of the record exerts absolutely no dampening iniiuence on the diaphragm so that, in so far as the record is concerned, the diaphragm can vibrate with a free aperiodic movement.

lin Figure 4 I have illustrated a modified arrangement of recording mechanism employing a vibrating electrode in the form of a swinging needle 104. The upper end of this needle is pivoted on a pin or screw 105 extending thru a depending lug on the trans-l verse bar 106. The diaphragm 86 has connection with the needle 104 thru an insulating rod 107 which has a pivotal connection 108 with the needle in close proximity to the piv-l ot 105. The bar 106 is suiiciently rigid to prevent it taking up any of the vibrationl of the diaphragm 86 and the ends of this bar are mounted in insulating bushings 109 carried in supporting brackets or lugs 111. The vibrating needle 104 preferably makes connection with the high potential circuit through the bar 106, as will be obvious from the preceding embodiment.

The lower end of the needle has vibratory motion across a. stationary electrode 112 -along which is guided the tape t. The upper surface of this stationary electrode is curved concentrically with the oscillatory movement of the needle so that the needle tip will remain at a uniform spacing from the electrode 112. The tape t may be made to assume this concave curvature by any suitable forming or guide means disposed above the electrode adjacent the plane of the needle 104. Flanges 113 along each edge of the electrode 112 confine the tape to a definite path relative to the needle 104, and insulating strips 114 along the inner side of the flanges pre'- vent the spark from jumping-to the flanges when the needle oscillates in close proximity thereto. I have not deemed the illustration of the reels or other mechanism for causing the travel of the tape across the electrode 112 necessary as such will be sufficiently apparent from the preceding embodiment.

As described in the previous form, the parts are constructed very light to minimize inertia and avoid damping the diaphragm 86. It will be apparent that by reason of the great multiplication of movement, comparatively slight vibratory movements of the diaphragm result in a considerable amplitude of movement of the sparking needle 104. This needle may be damped, if such is found desirable, by the use of a vane or any other suitable means. j

The successive perforations defining the undulating record wave are illustrated in exaggeration in Fig. 5, wherein a portion of the record tape is shown. The linear length of the wave alone' the tape for a given sound vibration may be varied by regulation of the tape speed during the recording operation. In the reproduction the rapidity of the lecture, or the tempo of the selection, can be obviously varied thru a wide range by control of the tape speed. The tape may be of any suitable material, being preferably of a thin grade of paper, however, of just sufficient tensile strength to withstand the feeding or pulling tensions. This tension is comparatively light so that a comparatively thin paper can be used, even approaching that of a comparatively light grade of india paper. It will beV apparent that if the tape should be torn completely across, no material injury is done, as the asting of the two ends together could only a ect a comparatively few number of vibrations, which would be practically imperceptible in the rendition of the record. Each edge of the tape may be reinforced by folding the margin back upon itself, or by pasting or confining a string in each edge, whereby these reinforced edges sustain the pulling tension and the intermediate web portion can be made correspondingly lighter.

In Figure 6 I haveillustrated a portion of my improved record tape produced by still another method of electrical recording. In this method the wave record is produced in profile along one or both edges olf the tape. This may be accomplished by making the frequency of the spark discharge so high that the successive perforations will form in effect a continuous slot or cut so that the edge of the tape can be easily torn'away, leaving the wave in profile. -Another method is to employ a continuous current arc which will burn the wave record as a continuous line or slot. The modification of the sparking electrodes for drawing and sustaining such an arc will be obvious to one skilled in the art.

The present method also has unique application to the production of talking moving pictures owing to the fact that the record may be embodied directly in the fieXible tape7 or strip of film instead of in a separate sound record. Either method may be employed within the scope of the invention. By widening t-he ordinary motion picture film and tracing the sound record along one or both sides thereof, absolute synchronism can always be maintained between the pictures and the audible reproduction. An exemplary form of this arrangement is shown in Figure 7 wherein the exposures 175 are formed along the left side. The perforations are cut by a high voltage spark of such low amperage that there is no danger of igniting the film, or the edge of the film may be treated to prevent ignition. As an alternative expedient the recording may be done while the film is subjected to a cooling blast of air or other gas or while the film is immersed in a shallow bath. To allow for the intermittent motion of the film, a portion thereof can be arranged for` continuous travel thru the reproducing mechanism at a speed identical with the aggregate or effective speed of the film thru the projector, the portion which is being audibly reproduced being preferably comparatively close to the portion beingprojected. The exposure of the film and the recording of the sound waves may be performed simultaneously, but at different points along the length of the film, by correlating the exposure camera and the sound recording mechanism for joint operation.

Instead of securing the variation of resistance in the reproducing lor transmitting circuit thru the undulating form of the line of perforations, such can be secured by variations in the sizes of the perforations. This meegaan practice of varying the sizes of the perforations has been suggested in connection with Fig. 2 for expression purposes, but it will be apparent that if enough variation can be secured this practice may be utilized for producing the sound itself. lVith such a record the series of perforations could be in a sub; stantially straight line, the variation in resistance being obtained by the greater or lesser current flow thru the larger orfsmaller perforations. Apparatus for producing this character of record is diagrammatically illustrated in Fig. 8, wherein the vibrating electrode is designated -180 and the stationary electrode 181. 1n this instance the vibratory electrode is mounted to vibrate towards and away from the tape t andelectrode 181. It will be apparent that a minute variation in the length of the striking gap between the electrodes 180 and 181 will vary the resistance of the high potential circuit thousands of ohms. Accordingly, the length of the gap will exert a material control over the current flow in the spark discharge andthe size of the f perforations will be influenced substantially entirely by the volume of current iiow in the spark discharge. Thus, when the electrode 180 vibrates into close proximity to the tape, a fat high amperage spark will be drawn which will perforate or burn a com-- paratively large hole in the tape. Conversely, when the electrode is vibrated to a point relatively remote from the tape the spark discharge will be lean and of a comparatively low amperage so that the perforation will be considerably smaller. in the apparatus shown 'these perforations will be in a suhstantially straight line in the tape, although it will be apparent that a combination of the two theories may be employed, if desired. rlhe vibrating electrode 180 may be connected to a diaphragm thru a multiplying system of leverage, as in t-he previous embodiments, although for the purpose of illustrating another use of the present method of recording l have deviated from this showing and have illustrated the electrode as being responsive to current oscillations set up in a wireless receiving circuit. The sensitivity of the pres-A ent method of recording vibratory movement adapts it particularly to use in the form of a recording instrument for recording wireless telephone or telegraph messages. In this relation, the vibratory elect-rode is made responsive to an electromagnet 182 which is substituted in the place of the head phones or loud speaker of a conventional receiving circuit. @ne or more stages of ampliiicationmay be employed in this receiving hook-up, if desired, but the need for a highly amplified current flow thru the electromagnet 182 is not imperative because of the small inertia of the vibrating electrode 180.

It will be understood that this same electrical actuation may be employed for operating` the electrode stylus in the constructions shown in Figs. 1 and 4.

While l have referred to only one record or line of perforation as being produced during the recording operation, it will`be apparent that a number of such records or lines of perforations can be produced during such recording operation for different purposes. For example, one record may be produced by such mechanism and under such tuning as to be an accuraterepresentation of the pitch of the sound waves; another record may be devoted to reproducing the amplitude or volume of the source of sound, and other records may be devoted to reproducing other characteristics of the sound. rlhese several records may be embodied in one record tape, if desired, for simultaneous reproduction through one or a plurality of reproducing d'evices. Y f

It will be obvious that numerous modifications Aand variations can be made from the embodiment herein shown and described, without departing from the essence of the invention.

l claim:

1. ln apparatus for recording vibrations, the combination with a moving record surface, of a movable electrode supported in proximity to said record surface but out of Contact therewith, mean-s responsive to the vibrations to be recorded for actuating said electrode, andan electrical circuit impressing a sparking potential on said electrode whereby sparks will be caused to jum the gap existing between said -movable e ectrode and the. record surface to form the record therein.

2. in apparatus for recording impulses, the combination with a moving record surface, of a stationary electrode positioned on one side of said record surface, a movable electrode supported in proximity to the other side of said record surface but out of contact therewith, means responsive to the vibrations to be recorded for actuating said movable electrode, and an electrical circuit for impressing a sparking potential on said electrodes, whereby sparks will be caused to jump the gap existing between said movable electrode and the record surface to form a spark-cut record in the latter.

3. lin apparatus for recording sound, the combination with a moving record surface, of a stationary electrode positioned on one side of said record surface, a movable electrode supported in proximity to the other side of said record surface but out of contact therewith, an electrical circuit for'impressing a continual sparking potential on said electrode during theV operation of the apparatus to form a substantially continuous spark-cut record in said record surface; and means responsive to the sound to be recorded for actuating said movable electrode for between said electrodes and form a perforated record in said tape, and means responsive to the sound to be recorded for oscillating said movable electrode.

5. The method of recording vibrations,

'impulses and the like, comprising supporting a movable electrode in proximity to but out of contact with a record surface, passing a substantially continuous discharge of electric sparks between said electrode and said record surface, and actuating said electrode in accordance with the vibrations or impulses to be recorded.

6. The method of recording vibrations, impulses andthe like comprising supporting a movable electrodein proximity to but out of contact with a record surface, passing a substantially continuous discharge of electric sparks between said electrode and said record surface during travel of the latter, to form a substantially continuous spark-cut record therein, and actuating said electrode in accordance with the vibrations or impulses to form sinuations in the spark-cut record.

7. The method of recording vibrations,

I impulses and the like which comprises causing a record surface to travel relative to. an electrode-stylus but out of contact therewith, passing electric sparks between said elec.- trode-stylus and said record surface, and V1- brating said electrode-stylus in accordance with the vibrations or impulses to be recorded.

8. The method of recording sound which comprises causing a record surface to travel' relative to an electrode-stylus associated therewith, passing an electric current directly between said electrode-stylus and said record surface to form a sound record in the latter, and vibrating said electrode-stylus in accordance with sound vibrations relative to the path of travel of said record surface to produce a `record having lateral undulations substantially transverse to the path of travel of the record surface.

9. The lmethod of recording sound which com rises drawing an electric spark from a spar :ing electrode to perforate a traveling record medium, and causing the sound vibrations to vibrate said sparking electrode.

10. The method of recording sound which comprises drawing an electric spark between two sparking electrodes, moving a recording rated by the spark discharge, and causing the sound vibrations to vibrate said sparking electrodes relative to each other.

11. The method of recording sound which comprises drawing an electric spark from a sparking electrode, moving a recording medium to be perforated by the spark discharge, and causing the sound vibrations t'o oscillate thc spark discharge across the recording medium.

12. The method of recording lsound which comprises drawing an electric spark between two sparking electrodes, moving a paper tape between said electrodes to be perforated by the spark discharge, and causing the sound vibrations to produce a relative oscillation between said sparking electrodes.

13. The method of recording sound which comprises producing an electrical discharge between two electrodes, moving a tape record between said electrodes, and causing the sound vibrations to vibrate one of said electrodes relative to the other for producing a variable sound record in said tape.

14. The method of recording sound which comprises supporting a movable electrode in proximity to but out of contact with a record surface, passing a substantially continuous discharge of electric sparks between said electrode and said record surface, producing current undulations in an electric circuit corresponding to the sound undulations to be recorded, and utilizing said current undulations to actuate said movable electrode for forming undulations in the spark-cut record.

15. The method of recording sound which comprises producing fluctuations in an electric circuit corresponding to the sound un-1 dulations to be recorded, and utilizing said fluctuations to control the actuation of al spark recording stylus.

16. The method of recording sound which comprises producing current undulations in an electric circuit corresponding to the sound undulations, and producing relative movement between a sparking electrode and the record surface in accordance with said current undulations.

17. In combination, a recording member adapted to be maintained out of contact with the record surface, means establishing an electrical discharge between said recording member and said record surface, and sound responsive means for producing relative motion between said recording member and the record surface.

18. In combination, a record surface, elecf trical means comprising a` sparking electrode adapted to have motion relative to said record surface, said sparking electrode producllO A ing the record by impingement of the sparkV electrode, a relatively movable electrode, and means for moving a record tape between said electrodes, a circuit for impressing a sparking potential on said electrodes, and a sound responsive member connected to said relatively movable electrode. v

20. In combination, a relatively stationary electrode, a relatively movable electrode, means for drawing a record tape between said electrodes, a circuit impressing sparking potential on said electrodes for causing sparks means for drawing a record tape across said stationary electrode, a movable electrode pivoted adjacent one end and having its free end adapted for swinging motion across said record tape in spaced relation thereto, a diaphragm operatively connected to said electrode, and a circuit for impressing a sparking potential on said electrodes.

26. A sound reproducing record comprising aV paper tape having a sound record formed therein as an undulating line of spark to perforate said record tape, and a dia- )cut perforations.

electrode, aA movable electrode pivoted adjacent one end for swinging movement in a plane transverse to said paper tape, an electricmcircuit connected to said electrodes for impressing a sparking potential thereon, and a diaphragm connected to said movable electrode for actuating the latter, motion of said electrode causing the free end thereof to approach and recede from` said "paper tape to shift the pointV of minimum sparking distance transversely across the paper tape.-

23. 4In combination, a moving record surface, a movable electrode pivoted adjacent one end for swinging movement in a plane transverse to the path of travel of said record surface, an electric circuit connected to cause a sparkdischarge to occur between said mov- 27. A sound reproducing record comprising a record surface having a sound record formed therein as an undulating line of spaced perforations cut by an electric spark. In witness whereof, I hereunto vsubscribe my name this 29th dav of March, 1922.

. CAMERON A. WHITSETT.

able electrode and said recordsurface, and y sound responsive means connected to actuate said electrode, the motion of said electrode causing the free end thereof to approach and recede from said record surface toshift the point of minimum sparking distance transversely across said record surface.

24. In apparatus for-recording vibrations, the combination with a moving recordksurface, of a movable'electrode supported in proximity to said record surface but out of contact therewith, means responsive to the vibrations to be recorded for actuating said electrode, an electrical circuit Vimpressing a sparking potential on said electrode whereby sparks will be caused to jump the gap existing between said movable electrode and the record surface to form the record therein, and damping means for controlling the movement of said movable electrode.

25. In combination, a stationary electrode, 

